1. Field of the Invention
This invention relates generally to the production of dielectric thin films and the application thereof to a specific kind of electronic device. More specifically, this invention relates to a process for producing dielectric thin films by a vapor deposition technique making use of laser beams and a pyroelectric type of sensors including dielectric films produced by such a process.
2. Background Art
So far, thin films of inorganic dielectric materials such as Pb-containing perovskite-type compounds used for sensor head parts, magnetic recording media, etc. have been prepared by magnetron sputtering, radio-frequency (RF) sputtering, chemical vapor deposition (CVD for short) or other vapor-deposition techniques.
However, dielectric thin films obtained by the conventional film-forming techniques are likely to be randomly oriented; when it is intended to obtain crystallized films with c-axis orientation in an as-deposited state, it is required to increase a substrate temperature to 600.degree. C. or higher, which makes it impossible to form them directly on such devices as Si-CCD or MOS-FET.
Another problem with the prior art film-forming processes, which are generally carried out at an oxygen pressure as low as 0.01 Torr or less due to restrictions imposed by the equipment used therefor or by the principles thereof, is that at such a low oxygen pressure there are compositional deviations in the deposited films due to a difference in equilibrium vapor pressure between target elements.
It is therefore an object of this invention to provide a process for producing dielectric thin films which are fully oriented with the c-axis even when prepared at a low substrate temperature and so are of high crystallinity.
It is another object of this invention to provide! a process for producing dielectric thin films which are free from such compositional deviations as found in the prior art processes.
It is a further object of this invention to provide a pyroelectric type of sensor having on the drain electrode of a MOS element a film of ferroelectric or pyroelectric material which is fully oriented in the c-axis direction and crystallized.